1. Field of the Invention
The present invention relates to a multiplex writing implement, and more particularly to a multiplex writing implement comprising a plurality of writing elements, at least one of which is a mechanical pencil, and whose writing tips can be alternately projected and retracted from the top opening of the front barrel section thereof; and an eraser which can be projected and retracted from the rear end of the cap thereof.
2. Description of the Related Art
Various kinds of writing implements have been proposed and provided which include plural writing elements, at least one of which is a mechanical pencil, and whose writing tips can be selectively projected and retracted from a top opening of a front barrel, namely a multiplex writing implement.
The present applicant has made several proposals relating to the aforesaid multiplex implement.
Of these proposals, there is disclosed a Japanese Utility Model Laid-Open Publication No. sho-64-3419 (published in 1989), which will be referred to as a first prior art example hereinafter. A multiplex writing implement in accordance with the first prior art example includes two writing elements each having a sliding piece at the rear end thereof. A guide cylinder having guide grooves for guiding these writing elements is provided securely fixed to a front barrel section of the device to contain and cover these writing elements. The implement is also provided with a cylindrical cam having at its front end a slanted cam surface which comes in sliding contact with the aforesaid sliding pieces, and a knocker at the rear ends thereof. The cylindrical cam can move in an axial direction with respect to a cap and rotate integrally with the cap in a circular direction. With this arrangement, the two writing elements can be selectively projected and retracted from the top or front opening of the front barrel section by rotation of the cap with respect to the front barrel.
The implement according to the first prior art example, however has a drawback, that is, it is difficult to take out the knock cover when an eraser is to be used.
Another proposal is disclosed by Japanese Utility Model Laid-Open No. sho-60-120889 (published in 1985) which will be referred to as a second prior art example herein. A multiplex writing implement according to the second prior art example, is structured such that a crown-shaped member projected out from the rear end of a cap is rotated to allow an eraser to project and retract.
The second prior art example has an advantage in that the drawback of the first prior art example, stated above, can be eliminated, but the implement of the second prior art example requires numerous metal components in various parts, and each component has a complicated structure, resulting in high cost.
Moreover, in the multiplex writing implement of the second prior art example, the crown-shaped member projected out from the cap is hard to hold with fingers due to its shortness, thus giving rise to difficulty in projecting and retracting the eraser.